This invention relates generally to a piston for a pump and, more particularly, to an arrangement for a disposable plastic pump for dispensing flowable material.
Pump assemblies for fluid dispensers are well known. Such pump dispenser includes those invented by the inventor of this present application including those disclosed in U.S. Pat. No. 5,165,577, issued Nov. 24, 1992; U.S. Pat. No. 5,282,552, issued Feb. 6, 1996; U.S. Pat. No. 5,676,277, issued Oct. 14, 1997 and U.S. Pat. No. 5,975,360, issued Nov. 2, 1999, the disclosures of which are incorporated herein by reference.
These fluid dispensers share a common characteristic that a piston is axially slidable in a chamber with the piston carrying a flexing disc which disc is adapted to deflect away from the chamber walls on movement of the piston in one direction in the chamber. The present inventor has appreciated that a disadvantage with such known piston pumps is that the force required to move the piston in a direction to deflect the flexing disc and permit fluid to move past the flexing disc can be substantial and may exceed standards set to accommodate handicapped persons. The forces required to move the piston can significantly increase with increased viscosity of the fluid.
The present inventor has appreciated that a further disadvantage with such known piston pumps is that difficulties are encountered when pumping fluids containing particulate matter. Hand soaps are known which include solid particles such as pumice, sand and other solid particulate matter mixed with liquids to provide a slurry-like composition which is fluid. The solid particles may or may not be held in suspension and, typically, the solid particles are not in suspension, however, the mixture has sufficiently great solids that the liquid merely fills spaces between the particles and the slurry has a relatively thick paste-like consistency.
In the use of known pumps with the piston carrying a flexible disc, the liquid in the mixture has been found to selectively flow past the disc with the disc restricting flow of the solid particles therepast. Therefore, due to limited deflection of the disc, the liquid comes to be removed and a matrix of solid particles with liquid removed develops upstream of the disc forming a plug which restricts further flow.
To at least partially overcome these disadvantages, the present invention provides a piston for a pump in which on the piston being moved in one direction, a disc tilts out of a coaxial sealed orientation with the chamber to assist in permitting fluid flow therepast, preferably, the disc tilts by reason of the stem of the piston being deflectable on the piston being moved in the one direction.
An object of the present invention is to provide a nozzle for a fluid pump which facilitates dispensing viscous fluids such as relatively thick hand soaps, honey, ketchup, mustard and other fluids with a high viscosity and other flowable mixtures such as slurries and pastes incorporating solid particles.
Another object is to provide a pump adapted to dispense flowable materials consisting of dry particular matter and dry flowable powders.
Another object is to provide a piston for a pump assembly which piston is adapted to dispense viscous fluids and may be formed as a unitary piece of plastic for ease of disposal.
Accordingly, in one aspect, the present invention provides a pump for dispensing fluids comprising:
a piston-chamber forming member having a cylindrical chamber about a chamber axis, the chamber having a cylindrical axially extending chamber wall,
a piston forming element received in the piston-chamber forming member axially slidable inwardly and outwardly therein;
said piston forming element having a head disc and a base,
the head disc disposed coaxially about a disc axis and extending radially outwardly to a sealing edge portion circumferentially thereabout,
the head disc coupled to the base for tilting of the head disc between a first coaxial sealed orientation and a second tilted unsealed orientation,
in the first sealed orientation, the head disc is orientated with its axis coaxial the chamber axis and the sealing edge portions engaging the chamber wall to prevent fluid flow therepast in a first direction,
in the second unsealed orientation, the head disc is orientated with its axis at an angle relative the chamber axis and the sealing edge portions permitting fluid flow therepast in a second direction opposite to the first direction.